Pulse testing apparatus



A. w. CLEMENT 2,680,11 PULSE TESTING APPARATUS June 1, 1954 Filed Oct. 9, 1950 8 Sheets-Sheet 1 I INVEN TOR.

M a I m June 1, 1954 A. w. CLEMENT 2,680,161

PULSE TESTING APPARATUS Filed Oct. 9. 1950 8 SheetsSheet 4 GE NERATOR 50 39 ALTERNATOR 5| 324 COUNTING CHAIN 52 Tll FIG.3

IN VEN TOR. ART H UR WARD CLE MENT BY 4 mrw- ATTYS June 1, 954 A. w.cLEMN1-' 2,680,161

PULSE TESTING APPARATUS Filed Oct. 9, 1950 8 Sheets-Sheet '5 TRAIN seousu c CHAIN INVEN TOR. ARTHUR WARD CLEMENT ATTYS.

ATTYS.

8 SheeTs-Sheet 7 FIG.6-

SWBD.

IN VEN TOR.

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nfl 3 9 w J v 8 Q E mm 4 6 m u 4 F m H L O m T 5 5 m 9 2 .r 4 o 0 5 M5 M P v Mo H 52m |8 m B 2 N 2 N 20 l r U T U H T I T H P .n OP 1 0- O n T a 0.. T B m T U o. U U IIO 0 T 0 T 9 0 9 1+ June 1, 1954 Filed 001.. 9, 1950 TEST UNIT'.

Patented June 1, 1954 UNITED STATES PATENT OFFICE 2,680,161 PULSE TESTING APPARATUS Arthur Ward Clement, Galion, Ohio, assignor to The North Electric Manufacturing Company,

Galion, Ohio, a corporation of Ohio Application October 9, 1950, Serial No.

32 Claims. (Cl. 179-175.2)

of the desired party.

Successful extension of the call, responsive to the receipt of these impulses, is predicated upon the ability of the many automatic switches in the exchange to work in given time relations and in given time sequences. The ability of the automatic switches to operate in these proper time relations and sequences is, in turn, dependent upon the operating characteristics of each of the individual elements in each of the automatic switches.

In conventional automatic telephone systems, the impulses are generally transmitted by the dial the rate of ten pulses per second, the impulses each having a percentage break period of about 66 percent of the total impulse time. It is apparent that even slight variations in the speed and percentage break period of the pulses may cause faulty system operation, and it is therefore necessary in accomplishing successful exchange operation to maintain a fairly critical set of standards at all times for both the impulse transmitting and the impulse responsive units of the system.

In a conventional switch, for example (which is one of insure reliable and successful operation of the automatic telephone exchange.

It is apparent therefrom that the adjustment of the various operating characteristics of the switches or relays of an exchange is an extremely important and critical operation in achieving successful exchange operation; and it is the primary object of this invention to provide a portable type testing apparatus which to solve the numerous problems encountered in The testing apparatus of the invention in one of its uses is the answer to such need.

Installers on the job have also been similarly handicapped by the limited testing means which his eyes and ears to observe faulty operation of With the provision of the sim- Similarly, the Work of installers engaged in adding new switching equipment to an Each type of equipment, of course, has particular and individual maintenance problems. One of the most common type of equipment failure, in a mechanical switch type ofiice, for example, is experienced with the Variation of the operating characteristics of from being rather tedious and exhaustive, was inherently subject to failure due to human error.

A feature of the present invention is the manner in which the small portable test apparatus is operative to transmit variable type pulses as directory numbers (or otherwise) to various vacant lines of the exchange for routining and checking purposes. Not only are the tests accomplished more rapidly, but additionally the accuracy and reliability of the test is extremely conelusive.

Maintenance and service men assigned to relay equipment have a different type of problem. In relay equipment, operational errors, ecause of the highly developed nature of the relay equipment, will be cancelled out and the inactive equipmom; will be passed over without indicating to the subscriber or the maintenance men that a faulty condition exists. While these features are especially desirable in providing reliable service to the exchange subscribers, the passing over of sufficient inactive equipment may lead to troublesome situations in hich the faults are not demonstrated until some critical point is reached. As a result, as the equipment reaches this point a considerable amount of maintenance will be required and interrupted service may result.

Such occurrence may be anticipated and precluded by occasional use of the est equipment of the disclosure to assist in detecting the individual faults as they occur and before the chronic fault condition is reached.

The equipment is of further utility to the maintenance or service man who, having made an adjustment, desires a thorough routining and testing of the equipment to test its operation. With out thorough routining and testing, the service man can never be confident that his adjustments have successfully eliminated the trouble which previously existed, and by use of the test equipment of this invention an assurance that such adjustment is successful is obtained.

Further serious problems in the adjustment of telephone exchange equipment in the field have arisen in the adaptation of existing exchanges for use with inter-toll dialling, wherein the senders and trunks of existing equipment are necessarily adjusted to the standards and norms set up for inter-roll dialling.

A feature of the testing apparatus of the present invention is the manner in which the tests of the equipment to be adapted may be readily accomplished, and the adjustment of the existing equipment for use with the inter-toll dialling equipment may be eiiected in a simple and expeditious manner. This particular use of the testing device promises to be of great importance in the near future as inter-toll dialling networks are more extensively developed.

The foregoing are only a few of many general and broad applications to which the test equipment of the invention may be adapted, and are only a few of the many problems which are readily solved through the use of the test unit.

It is believed that the details of these various applications will become more apparent with ref erence to the following disclosures and drawings in which Figure 1A is a perspective view of the test equipment in its assembled state; Figure 1b to 4 inclusive, in their assembled form, disclose a schematic sketch of the test equipment elemerits; Figure 5 is a schematic sketch showing the manner of connection of the test equipment to test the switches of a nautomatic telephonic systern; Figures 6 and 7 illustrate, in block form, loop and single wire connections for the test unit and an exchange installation; Figures 8, 9, 10, 10c are illustrations in block of the manner of connection of the test unit in testing individual elements of various automatic switching members; Figure 11 is a schematic sketch of a balance test circuit for use with the test equipment; and Figure 12 is a schematic circuit sketch of a dial tone test circuit for use with the test equipment.

TABLE OF CONTENTS For purposes of attaining ready access to the description of the various portions of the equipment and the description of the various tests which may be performed with the test equipment, the following sectional headings are tabled at this point:

1. General test equipment application 2. General description 3. General operation 3.1 Set adjustment 3.2 Optional procedure subsequent to pulse adjustment 4. Circuit description 4.1 General circuit operation 4.2 Normal set condition 4.3 Pulse adjustment 4.31 Generator operation 4.32 Speed-percentage circuit operation 4.33 Metering 4.4 impulse transmission 4.41 Key settings 4.42 Initial circuit operations 4.43 Impulse generation 4.44 Alternator operation 4.45 Connecting chain operation 4.46 Sequence chain operation 4.5 Start-stop circuit 4.6 Cycling without testing 4.? Single cycle operation 4.8 Continuous pulsing to a seized stage 4.2 Manually controlled pulsing 4.91 Push button train start 4.92 Push button alternator control 5. in pulse measurement 5.1 Percentage measurement 5.2 Speed measurement Test for G relays Test for F relays 8. Test of repeater for pulse distortion 9. Test of selector for stepping characteristics 10. Balance test and dial tone modification 10.1 Balance test circuit 10.2 Dial test circuit 11. Conclusion 1. General test equipment application various following conditions and to provide the various following types of tests:

1. Control keys on a pulse measuring panel permits the adjustment of the pulses to be sent and measures pulses locally generated and/or received from an external point.

2. Generated pulses can be continuous, or form numbers having 1 to 5 digits.

3. The above generalities can be variously controlled.

(a) The outgoing line can be metallic loop or single wire (ground or battery drive) with a choice of 0, 500 or 1,000 ohms in circuit.

(12) The pause between the digits of a number (interdigital time) is adjustable from about 100 to 1200 milliseconds (national standard is 600 max).

(c) Digits can be individually sent by operating a push button, for casual progress through a switching system.

Calls arranged to be automatically re- (d) peated in cyclic fashion are and "non-test tested, hold the ful D. O. and gauge adjustments, using pulses to complete the adjustments; this practice also discovers shorted-turns in fast coils not evident with D. 0. tests.

7. The set can call from any line to any test line number and can 2. General description The pulse testing apparatus of the invention, in preferred embodiment, comprises a portable type unit which is of extremely light weight, and of a comparatively small size, the overall dimen sions being approximately 9 in. x 13 in. x 7 in.

All circuit control elements are the top side of the panels to provide purposes.

A removable cover 3 is used to protect the panel equipment 2 from damage during portage with cooperating the sides of the cover 3.

The control keys and knobs mounted upon the panels 2 are arranged to form a pulse control section 5, a test control section 6, a train control section i, and a pulse measuring section 8 (Figure 1).

be tested, the the testing apparatus being transmitted there over. v

A set of in the upper right terminals I2, hand corner of ventionally used in telephone exchanges. Extension of the connected power supply connected to the circuits of the test equipment is controlled by a battery key H. the test unit in the disclosed embodiment is shown as powered by a 48 volt D. 0. supply, it is to be understood that the equipment is readily converted for use with a volt supply.

The primary function to provide test pulses in the coverplate 2 for convenient accessibility as required. Similarly a drive relay to which transmits the electronically generated impulses over the interconnected circuits is mounted on the panel face by means of a plug-in socket connection. The relay 22 is thus readily accessible for adjustment and replacement purposes.

' the generated impulses, to

various manners is deterof the several equipment and in its stop position to interrupt the supply of potential thereto. A repeat key 26 optionally controls the equipment to effect repeated transmission of a predetermined digit or digits, a single transmission of that digit or digits or the transmission of a continuous string of pulses. A pulse key 28 controls the nature of the pulse to be transmitted, the pulsin loop controlled by the pulsing relay being normally open when the key 28 is in the break position and normally closed when key 28 is in the make position.

A two position locking hold key 25, a non-locking manual control push button key 26, and a shift key 23 provide means for manually starting successive transmissions of pulses. hhe functions of these keys will be more thoroughly brought out hereinafter.

Line current control may be effected by means of an out-line ohm key 29 which in its several positions varies the value of resistance to be included in the outgoing test pulsing loop. in-P- wire resistance key 39 alternatively connects high or low resistance in the P-wire circuit and in- P-wire battery key 32 alternatively connects positive or negative battery to the P-wire test conductor.

An important feature of the invention is the manner in which the equipment is operative to transmit groups or trains of digits in repetitive cycles. For the purpose of establishing the value of these digits a plurality of manually operated digit switches e a-3s inclusive are provided. The switches are each operative to ten positions which are identified in sequence by numbers 1-0 inclusive. Each of the switches 34-38 are enabled in the sequence of their arrangement whereby the setting of the first switch determines the nature of the first digit to be transmitted, the second switch determines the nature of the second digit etc. A five point switch 33, designated as the cycle switch, controls and determines the number of digits to be transmitted in each train. Ihus to transmit the number 3'78, the cycle switch is set on digit 3 to indicate the number of digits in the train; the first digit switch 32 is set at position 3; the second digit switch 35 is set at position '1, and third digit switch 36 is set at position 8. Ihe settings on the other two switches are of no consequence for the cycle switch 33 renders them ineiiective in the impuise transmission.

A series of thyratron tubes Ti to T22 mounted on the topside of the control panel for ready accessibility are important elements of the various control circuits. Thyratron tubes TH and Tit for instance are included in an alternator arrangement to the alternated impulses of the generator tubes T2! and T22. Alternator tubes TH and TM in turn are effective in controlling sequential striking of thyratron tubes Ti iW which in their sequence form a basic portion of an electronic counting chain unit.

Briefly, operation of the equipment to transmit a registered number comprises registering oi the number on the digit and cycle switches and operation or" the start key to the start position. The generator tubes generate impulses of a value commensurate with the setting of control potentiometers i3 and I9, and drives the alternator tubes Ti 1 and Tl2. As the alternator tubes advance the counting chain to the tube in the counting chain sequence which compares to the position set on the first digit switch 34. the first tube of a group of sequence tubes Tit- 226 fires and efiects operation of a stop tube Tl3 to momentarily terminate the operation of the generator pulsing tubes 2| and 22. he length of the pause established is adjust- 8 able between .12 and 1.5 seconds and is accomplished by adjustment of the pause potentiometer 40.

During this pause period, the counting chain tubes Ti iiii are extinguished and the generator tubes T2! and T22 and alternator tubes Ti! and H2 restore to a given starting point. As the pause period elapses, a start tube Tit fires and the generator pulsing tubes T2! and T22 once more operate the alternator tubes TH and 112. The counting chain tubes Tl-Tlil are responsively advanced to the tube corresponding to the setting on the second digit switch 35, upon which the second sequence chain tube TH operates the stop tube Ti; and extinguishes start tube it. A pause is once more introduced and the third registered digit is transmitted in a similar manner.

As the third digit is transmitted, cycle switch 33 being set at position 3, becomes effective and the equipment is restored. As will be shown hereinafter, the same generated pulses which operate alternator tubes TH and TB are also transmitted as digits and trains by the pulsing relay 22 to the equipment under test. It is apparent that variations in the operation or the equipment occur with movement of the control keys to various positions. For example, if the repeat key 2 1 is in the repeat position, the equipment under test is reseized and the registered train or digits is repeatedly transmitted in the manner described until stopped by operation of the start stop key 23.

As an aid to accurate adjustment of the testing and tested equipmen a pulse meter M which is graduated and calibrated to indicate the rate of receipt of pulses per second as well as the percentage break period of an impulse is mounted upon the control panel face. A measuring key is is adjustable to three positions, the key in its upper position connecting the meter M and associated circuits to measure the impulses received over the incoming terminals i2, i3 and it; the key R2 in its lower position connecting the meter M to measure the output pulses of the drive relay 22, and the key 42 is in its normal position completing a portion of the connection between the out terminals 9, it, ii and the pulse generator equipment.

A two position key 41 adjusts the meter M in its one position to read the impulse speed and in its second position to read the make to break ratio of the impulses. A meter key 48 and compensating knob 49 provide suitable compensating means for insuring meter accuracy with occurrence of variations of the value of supply voltage.

Tube test equipment including a tube socket 2-3, a fire button it and tube test keys 45 and ii are mounted on the control panel whereby the various tubes in the arrangement may be tested for strength and sensitivity, the readings being indicated by meter 4!.

3. General operation A more complete digest of the various genera functions of the equipment responsive to variation of the settings of the control keys H, l8 etc., is set forth hereat.

The test unit in its basic embodiment is an automatic dial which is adapted to send impulses at various speeds and which is operative to gen erate impulses having a controlled variable make to break ratio. The pulses may be generated continuously, or as individual digits, or as trains of digits, each digit being comprised of a predetermined number characteristics.

3.1 Set adjustment Adjustment of the prior to testing battery key H 25 to the Battery terminals l and a source of battery potential repeat position. I 6 are connected to I! position and the equipment is dition for operation.

Prior to the initiation of the transmission of pulses the meter is moved to its on in the standby con- 47 is operated to the repeat key 24 position. The percentage knob 58 is then adjusted until the meter reads the desired percentage break.

In adjusting the speed of transmission of the test key 41 is operated to the s position and the adjustment knob is returned to its normal position.

The circulator is conditioned to send pulses of an adjusted value.

3.2 Optional procedure subsequent to pulse adjustment At this point the control keys to their various positions permits or negative battery or with a loop circuit to operate by adjustment of key 32 to the 33, G or M positions. The resistance of the outpulsing circuit can be set for 0, 500, or 1000 ohms by proper operation of the out-line ohm key 29.

The in-P-wire resistance key 30 is operable totwo positions, the low resistance position and the high resistance position. In the low resistance position, a 500 ohm test relay is placed in series with the in-P-wire terminal 14 and is representaof impulses of preadjusted' in the order of 46-53 potential to the in-P-wire through the test relay of the equipment. In its optional position the key efiects of negative potential to the in-P-Wire through the test relay of the equipment.

The test relay to be disclosed more fully hereinafter may be optionally eiTective or ineffective through the operation of the in-P-wire test key 3i to either of its optional positions. In the test position the test relay contacts intervene between the final with the adjustment of the in-P-wire test key to the non-test position, the set operates independent or the test relay.

In use in the field to test a particular type of equipment having known pulsing norms, the foregoing keys are readily moved to their appropriate positions.

The manner of operation of the test equipment after setting of the keys to determine the line pulsing characteristics desired is determined by the control keys 23, 2t, 25, 26 etc. Operation of the start key 23 initiates operation cycle switches.

With the repeat key 24 in the repeat position the trains of impulses are repeatedly transmit ted, the equipment being operative to test the success of the call in reaching the desired destination if the in-P-wire test key is in the test position, and the equipment being operative to repeat With the repeat key 2 5 in the once position the train of digits is transmitted only once, and

the equipment is held until released.

By movement of the repeat key 2 3 to the continuous condition, continuous pulses are transmitted to test the equipment at the particular stage to which it had been sent.

In the event that manual control of the equipment is deemed desirable, manual button 26 may be used to accomplish two distinct manual controls:

(1) With key 25 hold it start tube control trols manual start of bar;

(2) With key 25 in the normal key 28 in the alternator control power key it in the heat position, manual key 26 permits observation of the alternator, chain tubes and associated relay performances, the start key 23 operated in either case.

The operation of the circuit arrangements in position and key position; key 26 con each digit of a given numposition, shift position and 4. Circuit description The various pulse generations and transmissions effected with operation of the aioredescribed control keys to the various positions are accon plished by a circuit arrangement set forth in Fig ures la to inclusive and which basically CURL." prises an impulse generator '50, an alternator 5!, a counting chain 52, a set of train switches 53, a cycle switch 50, a sequence chain 5 3, a startstop tube arrangement 55 and a set of control relays iEfl, 500 etc. Adritionally the arrangement includes pulse testing circuit means El which is operable to test the impulses as generated by the generator unit 50 or as received over the inco1ning terminals l2 and i3.

The control keys ii, 18 etc. have been described heretofore and further description at this point is not believed necessary. The contacts of the keys are shown in the position assumed when the keys are in their normally relaxed position,

Pulse generation responsive to proper operation of the control keys is efiected by means of a pulse generator which basically comprises a pair of tetrode thyratron tubes 300 and 305, respectively, of the type which is manufactured by the General Electric and marketed as a 5663. An associated RC network .llE, which is identified as a speed-percentage network, is adjusted by movement or the speed pulse adjustment potentiometer l9 and the percentage adjustment potentiometer [8.

The plate 301 of the thyratron tube 300 is supplied with positive battery potential in the order of 50 volts over conductor 08 through pulse relay 450 (shunted by resistance $03) when control key 208 is operated on. supplied through resistance 300 when the power key is operated to heat or on. The anodes 313i and 300 are interconnected by an anode capacitance 38?. which is in the nature of .05 mid.

Anode 30! of the first generator tube is also connected over a capacitance 33! which is in the order of .20 mfds, 10,000 ohm resistor 31? to the lower control grid 30'5 of the second tube. Plate 309 of the second tube is connected to control grid 303 of the first generator tube 300, over a i.

.20 rnfd. capacitor 303 and a 10,000 ohm resistor 3l3.

The second shield grids 302 and 308 of the generator tubes 300 and 305 are connected to their respective cathode circuits. The cathodes 304 and 306 of the generator thyratrons 300 and 305 are connected to negative battery over a 220 ohm resistor 3H and to positive battery over a 10,000 ohm resistor 319.

The speed-percentage regulating network 3W is connected between negative battery and the control grid circuits of tubes 300 and 305. The percentage control portion of the network comprises a pair of 7,000 ohm resistors sl m and 3140 connected in series with a variable resistor Plate 309 of tube 305 is 314?) which is variable between 0-500,000 ohms. The speed control portion of the network comprises a 5,000 ohm variable resistor 2H2?) which is connected in series with a 620 ohm resistor 332a. Negative battery which is connected to speed control resistance 3120. is in turn extended over resistances 3121), 314b, 310a and 3W0, tit and 313 to normally negatively bias the respective grids 303 and 301 of the generator tubes 300 and 305.

The speed-percentage network 315 is also connected to a starting conductor 2'50, which extends to grid 30? of the second generator tube 305 over a capacitor 3'18 which is on the order of .005 mid.

In the normal standby condition with the battery key I! in the on position, positive poten tial in the order of 1 volt is normally supplied to the cathodes 304 and 300, and positive potential in the order of volts is impressed upon the plates 30%! and Bill. The tubes are normally negatively biased by the RC network M5 to prevent firing thereof. The output side of generator 50 extends from the plate 30i of the first generator tube 300 over both conductor 00 to a pulsing relay its (22) and over resistance are and capacitor 380 to an alternator circuit 55. Resistance 310 is in the order of 10,000 ohms and capacitor 392 is in the order of .001 mfd.

The function of the alternator arrangement is to extend the impulses as received over alternative outgoing conductors (labeled odd and even in Figure 3) to the counting chain arrangement 52. Alternator 5i basically comprises two tetrode thyratron tubes 310 and 235 which are commercially available from General Electric Company as thyratron tubes 5663. Plate 31! or" the first alternator tube 3m is adapted to be energized by application of positive potential in the order of 50 volts over load resistance 365, and the plate 319 of the second alternator tube M5 is adapted to be energized by application of positive potential of 50 volts over conductor 213 and load resistance 368. The plates of alternator tubes 310 and 3 l 5 are interconnected by an anode capacitor 361, which is in the order of .10 mid.

The output side of the generator 50 is connected to an alternator input circuit comprising capacitor 385 and resistances 388, 30 and 385. Capacitor 386 is in the order of .001 mid. and resistances 33B and 385 are in the order of 100,000 ohms. Resistance 38!! is in the order of 47,000 ohms. The cathodes of the alternator tubes 310 and 3E5 are connected to negative battery over a resistance 38'! which is in the order of 620 ohms.

Capacitor 392 which is connected in the output circuit of generator 50 serves with resistance 3% as an RC filter which limits the peak voltage of the generated spikes and widens their time bases; it also filters the stray capacitor cross fires which may appear in the circuit.

An auxiliary biasing circuit for the first alternator tube 3H0 extends over conductor 21! and resistance 380 which may be in the order of 270,000 ohms. The auxiliary starting circuit extending to the grid 313 is in effect a zero start control which insures that the first generated impulse is extended over the odd conductor to the counting chain 52.

The output conductors of the alternator El labeled odd and even respectively extend to a counting chain 52 which comprises a series oi ten tetrode th iatron tubes, of the type heretofiore described which are arranged in a given 13 predetermined sequence. Each of the thyratron and their selected counting tubes as successive tubes 320 to 365 inclusive have two control grids. digit counts are made.

One of the control grids of each of the odd num- The plates or anodes, such as Ml, of the sedlfielentlatlng circuit to the odd d1 ive conductor 5 ranged to be n rlz d t a p t n l of ppr x and one of the control grids of each of the even mately 50 volts positive over a common conductor numbered tubes is connected over a d ife er- 274. The cathodes such as 445 of each of the tiating circuit to the even drive conductor The sequence chain tubes are biased at approx mately differentiating circuit for the first tube 326 com- 6.4 vol s posi iv by ind vidu l as i d n prises a capacitor 39 in the order of .005 mid. works, which comprise a network of series reand a resistor 396 in the order of 270,000 ohms. sistances such as '466, 467, 468. The upper grid The differentiating circuit for the other count- 642 of the first sequence chain tube 30 is also ing chain tubes comprises a capacitor such as biased at 6.4 volts. 395 in the order of .005 mfd. and a resistor 3:)? The lower grid of the first sequence tube did in the order of 47,000 ohms. is negatively biased by its individual network The plates of the tubes in the counting chain and resistances 4|! and H8 Each of the lower sequence are adapted to be energized by a pogrids such as 448 433 etc of the second to fifth tentlal of approximately 50 volts as appl ecl over sequence tubes are biased through a resistance 25 Cathodes, such as 323 etc., of each of the which is connected to the resistance network biased by a potential to approximately 6.4 volts as 348 of tubes two to five in the sequence is in with respect to the negative battery terminal, the order of 2.0 volts, whereby the grids are made such bias being effected by a plurality of indiapproximately 4.4 volts negative with respect to vidual resistance networks comprising a resi-sttheir cathodes. ance such as 393, which is in the order of 47,000 The upper grid of the second to fifth tubes ohms, a resistance such as 39 1, which is in the in the sequence are at negative battery potential order of 4700 ohms, and a resistance, such as and accordingly approximate y -4 Volts Rege- 395, which is in the order of 2200 ohms. tive with respect to their cathodes.

The second or other grid such as 328, 333 of It is appa t om the ore oin that the fi st each of the remaining counting chain tubes 325, or the sequence tubes 440 is p d to Operate 330 etc a e connected to the individual netwith the appearance o a po Pulse p the inately 2.0 volts positive with respect to negative will raise from approximately 6.4 to 40 volts of battery terminal. which about 12.7 volts will appear across the The second grid 322 of the first counting chain lower grid MS of the second tube 445 to render tube 320 is thus normally at zero volts with rethe grid MB of such tube 6.3 v. positive with respect to cathode and the second grids of the spect to its cathode. In summary, aprimed tube second to t nth tubes 325 to 365 are approxithus has its priming grid 6 3 v positive and its niately 4.4 volts negative with respect to their operat n d a -4 negative (each t a d cathodes. The first tube is therefore referred The second tube of the sequence is now primed to as normally primed for operation. The first for operation and as the positive pulse (subspike via the odd lead rendering the first grid stantially greater than 6.4 positive) subsequently 323 suificiently positive to fire the tube. appears across the econd grid i l?! of that tube, A series of ten-position, train switches 545 that tube will strike to prime the third tube to are, inclusive, control the point of advance- 450. Thus each tube in firing primes the sucmerit of the counting chain. The cathode, such ceeding tube in the sequence. It should be obas are of each of the counting chain tubes 320 so served that the RC combinations of 1.8 megohms to inclusive are connected to the point on and a .01 mid. condenser to battery delays the each of the switches which corresponds to its rise of potential of the firing grid of tube 3 25 number in the sequence. For example, tube 320 (for example), by being directed through posi- (the first tube in the counting chain) is contion 1 of the second train switch (420), tube 455 nested over conductor 400 to point i of each of 5.) does not fire at this time. This is required bethe switches M5 to :335 inclusive, tube 325 (the cause of the inability to use a definitely separated second tube in the counting chain) is connected odd-even drive, with which primed grids can over conductor Mil to the second point of each reach the primed value instantly.

of the switches, etc. The cathodes of each of the sequence chain The operating arms of each of the train cc tubes 440-460 are also connected to a start-stop switches 53 is connected over an associated difcircuit 55 by a rectifier s7: and a differentiating ferentiating network to an associated tube in a network comprising a capacitor such as W2 and sequence chain as. The differentiating network a resistance tee. Capacitors such as 12 are in for tube 40 comprisin a capacitor Such 5 the order of .001 mid. and resistor set is in the which is in the order of .01 mid. and associated 05 order of 47,000 ohms.

resistance 4 is in the order of 270,000 ohms, which The start-stop control arrangement 55 comis conn ct d t a p n s ur of po nti l in prises a pair of thyratron tetrode tubes M5 and the order of 2.0 volts. Th difiere t netare or" the type described heretofore which are work for tubes cre ses comprise a capacitor such operative to alternatively control th stopp ng as its in the order of .01 mid. and a resistor and starting of the generator unit 5t. such as 423 in the order of 47,000 ohms. The plate 276 of the stop tube 575 is positively The sequence chain tubes M0 to 4550 inclusive energized over resistance i -09 by a potential of comprise a series of five tetrode thyratron tubes approximately 50 volts positive and the plate 48! of h yp h r or describ d which ar operof the start tube ist is normally arranged to be ated in sequence via the associated train switches energized through reset relay 250 over conductor 212 by positive battery of approximately 50 volts positive. The plates 4M and 215 are connected by capacitance member 688 which is in the order of .05 mid. The cathodes sis and iial of tubes M5 and 480 are connected to a negative potential as are the upper control grids 5?? and 82.

The lower control grid 483 of start tube are is arranged to be biased by a negative poten (derived from a 1.0 mfd. condenser) applied over a resistance 08?, which is in the nature or 10,000 ohms, and conductor 2'50 which extends to the control relay sections and the control irey section of the equipment. When start the release relay 150, the 1.0 mid. condenser slowly charges positively until the firing of start tube 480 effects operation of the reset relay initiation of the impulse generation. Starti g of the equipment may thus be influenced by control of the proper combination of control keys to control the start tube 480.

The lower control grid 418 for the stop 415 is connected to the cathode output circuit of each of the sequence chain tubes whereby the tube is arranged to strike with firing of any one of the sequence chain tubes. With striking of the stop tube 015, the start tube are rendered non-conductive through the intercoupleal plate arrangement including capacitor 088.

Each of the cathode circuits of the S$jLiGPC; chain tubes M to 460 are connected to sponding sequential positions on a five poin' switch 55, the cycle switch being in turn connected to a final relay 280. As the sequence chain advances to the point in the sequence cor-- responding to the setting on the cycle circuit is extended to the final relay nate the cycle. A time period of delay the retransmission of the registered nurses; which has been set upon the equipment is efiected on use of the equipment in its cyclic ca pacity to provide suitable operating periods for the equipment under test. The pause period basically efiected through the means oi a pause adjustment network including capacitor and resistances 250, 251, and 259, capacitor 264 being in the nature of 1.0 mid. and resista 256 in the order of 10,000 ohms, 25? in the on of 2200 ohms, 259 in the order of 100,:20o ohms and 253 in the order of 100,000 ohms.

The control of the equipmentreset following the transmission of each or the digits of a numher is effected through the operation of a final relay 200 and reset relay 250. Test relay is optionally connected via the in (P) terminal to the equipment under test and is provided for indicating success of test. A release relay is adapted to effect release or the tested equipment at termination of a cycle (non-test) or with the operation of the test relay 2 1-0 (test) follow ing the termination of the cycle.

A pulse testing circuit 51 basically comprises a diiierentiating circuit and integrating circuit, and a resistance potentiometer i li which is com mon to both of these circuits in their arrangement with a meter M. The testing equipment is arranged to be connected over a meter key it, a percentage-speed test key :21, and a measuring key as to test either the impulses as provided by the test equipment or the impulses as transmitted by the equipment under test.

The in-out conductor Hi3 from either the test or tested equipment extends over contacts ifii (for speed) or 122 (for percent break) of the test key M to a choice of a diiierentiating circuit (contact 121), or a current limiting circuit (coniii) tact I22) common to both is an integrating circuit.

The differentiating circuit tests the rate of arrival of the impulses and basically comprises a resistance element 536 which is in the order of 700 ohms, a capacitor 100, in the order of 3 mid. connected series with resistor 31, or" approximately ohms terminating at a variable potentiometer Hi! to negative battery.

The current limiting circuit for percent break tests comprises calibrating rheostat 538 (about 10,000 ohms) and resistor 38 in the order of 10,000 ohms terminating at potentiometer lei.

An integrating circuit is common to the speed differentiating and percent break current limiting circuits as they meet at the variable potentiometer lei, which may have a range or" from 0 to 200 ohms. The integrator circuit comprises rectifier Hi0 (short circuited during percent break tests), capacitor it?! which be in the order of 500 mid. and resistor Hi5 which may be in the order of ohms.

The detailed operation of the elements in combinations as determined by the settings or the control keys will not be set forth.

2.1 General circuit operation The manner of operation of the test device in its various applications is believed to be best approached by a disclosure of its use in testing or routining conventional automatic telephone exchang equipment by repeated transmission of a series of digits to an idle line employing a pulse speed of say 10 P. P. S. with a per cent break of 60, conforming with the operating characteristics or the particular equipment under test (representing typical conditions in practice).

As shown in block schematic representation of Figure 5, the testing apparatus may be connected to test the switching equipment of an automatic telephone exchange by the interconnection oi driving leads 503 and 504 between the test equipment terminals 9 and I0 and the chosen line in the exchange which enters the input side of the line finder-selector link The connection of the input terminal it of the test box to the P wire of an idle line to be called, which is shown as point 234, provides the means for testing success of arrival. Thus, the test equipment effects the repeated transmission of the number 234 over the said calling line 503-- 50 1.

To accomplish such transmission, the set is first adjusted to the standby condition and then to generate a series of pulses at the chosen rate of speed and break percentage.

The outline ohm key 29 is then moved to a position which indicates the desired loop resistanoe (0,500 or 1000 ohms), the outline key 32 is moved to the M position (metallic loop), and the pulse key 23 to the break pulse position through contacts I31, the in P-wire test key ii to the test position (assuming usually desired polarity) and the in P-wire battery key 32 to negative to P-wire position, th cycle switch to position 3 (for 3 digits to be sent) the first digit switch to position 2, the second digit switch to position 3, and the third digit witch to position 4. The pause knob 25% is set for the value of pause desired between digits as determined by measurement at the terminal PT 253a (using separate measuring equipment) or by trial after set starts operating.

The start key 23 is then operated to the start position and the digit 234 is transmitted. The test relay 250 operates as the call is successfully ment. Pulses are also transmitted to the alternator unit 5| which synchronously generates and delivers pulses alternately to the odd and even which responds by advancing one tube in its sequence for each pulse received.

The number of effective.

Thus, with train switch 4I5 set at position two, as the counting chain 52 advances to the second tube, th train switch M5 effects the operation of its associated sequence 54, which in turn operates the stop tube 475 of the start-stop circuit 55 to terminate operation of the generator equipment 50.

The reset relay 25!] operates to stop pulses and prepare for transmission of the succeeding digit after the elapse of a predetermined time period having a duration as determined by the pause adjustment circuit 58.

Successive digits are similarly transmitted until the final digit (4) has been sent. At this time final relay 260 operates, seeking to operate release relay I50 but, due to the test condition setup, it must await th operation of test relay 240;

As digits 234 have ex'c pears on the P wire of line 234 and via the In-P terminal I 4 on conductor I12 of the test equipment operating test relay 240. The final relay is now able clearing the set and the exchange for the next Note that another call cannot start until the exchange has actually cleared (releasing 240), as will be indicated by removal ofpositive battery from the In (P) test terminal.

In the event of arrival failure, the release relay cannot operate and the set is static, the sequence chain remaining visibly fired. Failure of the exchange to clear also holds the set static, but the sequence chain is extinguished.

The recycling continues until a failure occurs or until the start key 23 is moved to the stop position.

42 Normal set condition of a vacant line on the switch board of the exchain tube 440 of chain 0 to operat the release relay,

18 The private wire of a station such as 234 is connected by conductor 502 to the input terminal I4 of the testing apparatus.

The plus and minus battery terminals 55 and It may be connected to a convenient source of potential, which in the given arrangement should be in the order of 46 to 53 volts (such as is normally available in conventional automatic telephone exchanges).

In preparing the set for operation, the battery to the heat position for apminute to permit ample time for filaments with a tial source to terminals I5 marked with negative battery symbol is connected to terminal i0, and with operation of the battery key 208 to the heat position positive battery is supplied over closed contacts 200 to I Frequently generator tube 305 is also rendered conductive, but this is immaterial at this moment.

Also, with movement of the battery key I1 to the heat position (and the start key 23 in the stop position) an operating circuit is completed for release relay #50 which extends from positive battery over the stop contacts 2I3 of the start key 2! I and the winding of relay I50 to negative battery. Release relay I50 is operated at this time to open contacts I54 and effect withholding of positive 503504 and to fire the stop tube 475 (by 100,000 ohms positive battery to its grid).

After the lapse of the prementioned heating time, the battery key I! is moved to the on position, whereupon positive potential is sup- 4.3 Pulse adjustment Prior to use of In the event that calibration of the unit is to be made from time to time, an approximately 50 the meter lI reads 10 P. P. S. measure check key depressed to break) is knob I38 is then It is to be understood that calibration of the equipment is not required with each use of the test unit, but only at comparatively infrequent occasions and then generally by the manufacturer.

In the transmission of pulses for test purposes, it is necessary that such pulses b transmitted at a predetermined rate of speed and that each pulse comprise a predetermined break to total ratio of duration. In the present equipment the so-called break ratio is indicated in values of percent break on the meter M3. The term percent break in the following description is reserved for actual measured open time of the contacts of pulsing relay IE or any other pulsing contacts under test (whether the contact be a break or a make type contact by construction) and regardless if it is normally open or closed when static.

Primarily, measurement and adjustment of the percentage of break to the total time duration of each of the pulses is accomplished by- (1) Operating the percentage speed test key 41 to the percentage position,

(2) Operating the repeat key 2 1 to the continuous position, and

(3) Adjusting the percentage slider l8 associated with the generator 50 until the meter reads the percentage break value desired.

With the adjustment of the control keys to the above positions, positive potential is applied over contacts 218 of the repeat key 2 and conductor 216 to the RC network associated with the generator circuit 50.

4.31 Generator operation As positive potential in the order of 50 volts is applied to conductor 216 over this circuit, a positive impulse is applied over capacitor fi'i'ii to the control grid 301 of the second generator tube 305 to render the grid 50! positive with respect to the cathode 305 which fires the tube 395, it being noted that the cathode 305 is at approximately 3.? volts in th standby condition of the test equipment compared to about one volt when neither tube was fired.

Additionally, with the appearance of positive potential on conductor 215, a positive potential appears at the slider on resistance 31% of the speed-percentage adjustment network 3'15, this potential to be varied to meet speed requirements and proportionally distributed via resistor 21th to the grids of tubes 305 and 305 to meet percent break requirements.

As the second generator tube 305 strikes, a potential reduction between the anode 358 and the cathode 306 thereof is effected so that the plate 303 of generator tube 305 is approximately 10 volts positive with respect to the cathode 3% by virtue of tube characteristics.

Also, with the firing of generator tube 305 an alternate path is completed from negative battery over resistance 31!, the now conductive tube 305, and resistance 380 to positive battery, whereupon the potential of the cathodes 304 and 306 is raised from one volt positive to approximately 3.7 volts positive, and the potential at plate 309 drops from 50 volts positive to approximately 10 volts positive to cathode.

With the drop of potential at plate 308 in the first instance, the reduction of potential is transmitted through capacitors 383 and 382 to the control grid 303 and the plate 30! respectively of the first generator tube 300 to thereby prevent firing of tube 300. the potential at control 2% grid 303 approa-c 'n 39 volts negative at this time and the plate voltage falling to approximately that of plate 300. 1

The potential of plate 30! of the first generator tube 3:30 rises quickly to 50 volts positive as condenser 3B2 charges up, and the sudden reduction in potential at the plate 301 is of too short a duration to permit operation of the pulsing relay I60 at this time.

As the potential applied to the grid 3113 rises following striking of tube 3%5 to overcome the 39 volt negative bias impressed thereupon, and there now bein 50 volts positive potential on the plate of generator tube 300, the control grid 303 eventually reaches approximately zero potential with respect to the cathode 355 and tube 300 strikes.

As generator tube 300 strikes, a potential drop between the cathode 304 and anode 30l of the tube occurs, and plate 30! drops to approximately 10 volts positive with respect to the cathode. Additionally, an operating path is completed for the pulsing relay H30 which extends from positive battery over contacts M0 or the battery key '11, conductor 93, pulsing relay $50, conductor i95, generator tube 350 and resistance 3' to negative battery. Pulsing relay 55 operates and at its contacts 162 opens positive battery over contacts H4, I55, I31 and H1 to the input lead I03 for the pulse testing equipment.

As the first generator tube 300 fired, the potential at the cathodes 304 and 305 and control grid 301 was in the order of 8 volts positive, and the plate 305 or tube 2 was therefore also raised to approximately 18 volts positive. With the reduction of potential at the plate 3M as the tube 300 fires, a pulse or kick is transmitted over capacitor 382 to the plate 300 of the second generator tube 305 to efiect the reduction of the plate voltage thereof to approximately 17 volts negative and thus effect the extinguishment thereof.

The kick pulse also appears at the control grid 301 of the second generator tube 305 and the potential at the control grid 303 drops to approximately 25 volts negative. Thus, with firing of tube 300, the impulse relay I60 opens its contact 62 to provide the open period of a generated pulse and generator tube 305 is extinguished.

As the second generator tube 305 is rendered non-conductive the potential of the cathodes 304 and 300 and the control grids 302 and 300 is kick reduced to approximately 5 volts positive. The potential at the plate 308 of the second generator tube 305 now rises relatively quickly to approximately 50 volts positive. The potential for control grid 30'! also rises, but at a less rapid rate as determined by the setting of the arm associated with variable resistance 1512b. As the potential at the control grid 30? approaches the game of approximately 5 volts positive, tube 305 res.

A corresponding reduction of potential between the cathode 306 and anode 309 is effected, and plate 300 drops to approximately 10 volts with respect to cathode. Additionally, the firing of the tube 365 causes the potential of the cathodes 304 and 306 and control grids 302 and 308 to momentarily rise to approximately 8 volts. The potential plate 305 also rises to approximately 18 volts.

The reduction of potential at the plate 309 as the tube 305 is rendered conductive, is transmit- 2i ted through the capacitors control grid 393 and plate 300.

383 as 382 to the 30l to squelch tube 4.32 Speed-percentage circuit operation The speed adjustment circuit 375 enables the generator circuit to generate pulses over a range from approximately 3 to 16 pulses per second. The variation of speed of pulse generation is deendent upon the adjustment of the resistance 31% in the network 3'15; the potential supplied toward the grids (subject to time delay in arrival) can more or less vary the negative bias of both tubes making both tubes less or more quickly reach their firing grid value.

Percentage adjustment enables the generator to be biased (without change of speed) so either tubes and hence relay I69 can favorone direction or the otherl% After the kicking impulse has been received over the capacitor 38! or 383 when one of the tubes is fired the charges in the capacitors 331 or 383 begin to build up to the firing point of their associated grids; as one or the other tube is standing fired, the other tube will reach its firing point after a time determined by the RC value of its grid condenser (381 or 383) and resistance path via its portion at 314?). Variable 37 5b maintains a time sum total proportioned to each tube.

The speed of pulse given is independent of the break to total ratio inasmuch as the total value of 312?) is very low to that of 3142 plus the added grid resistors and hence inappreciably effects any Therefore, moving the slider 3121) in the direction of the negative battery decreases the number of pulses per second and. moving the slider in the direction of the positive battery increases the number of pulses per second without relative change of the firing time ratio, tube to tube.

, It is apparent from the foregoing that the tubes 300 and 395 are alternately fired in a predetermined time cycle as effected through the adjustment of the arms 372D and 31th. The first generator tube 395 responsively controls the pulsing of the relay I66 and the transmission of positive potential pulses over resistance 311'! to the alternator unit 5 l.

4.33 Metering Following adjustment of the generator to pro following key and switch settings 22 vide the desired break or rate of receipt of measurement with the percentage-speed test key 41 to the speed position.

The pulse output of the pulse relay I 60 as it appears at the input over closed contacts I2l and meter key #58 to the integrating circuit associated with the meter 4| and an indication is provided of the rate of speed of the impulses.

As the respective speed and percentage adjustents have been accomplished, the repeat key 24 to the repeat position and the measto the normal 4.4 Impulse transmission I Having adjusted trains to simulate the single or mission of a directory number by a dial of a telephone instrument.

4.41 Key settings Assuming that the automatic telephone equipment i sending break pulses to a system having of the convenconditions, the

transmitting the phone exchange.

1. Outline key 32 is moved to the M 2. Outline ohm key 29 is moved to position,

3. Pulse key 23 is moved sition,

4. In P-wire test key 3! position,

directory number 234 to the teleposition, the 500 ohm to the break pulse po- 5. In P-wire battery key 32 is moved to the nega tive to P-wire position,

6. Repeat key 24 is moved to the repeat position,

7. The C cycle switch knob 33 is moved to position 3,

8. Train switch know 34 9. Train switch knob 35 1s connected to a vacant line of a switchboard to be tested, and

12. In terminal P i4) is connected to the private wire of the called line 234.

The connections board for a metallic loop drive as assumed above the start position,

16 pulses per second by lead I83- is now connected are effected in is moved to the test I 36 is moved to position 4.- Out plus and minus terminals 9 and 10 are equipment now automatically transmits 4.42 Initial operations The operation of the test circuit arrangements in accomplishing such transmission is set forth in detail hereat. With operation of the start key 23 to the start position, positive battery is applied to the plate of the second alternator tube 315 over a circuit extending from positive battery, over contacts 2I2, conductor 213, and resistance 36-0 to plate 3I9 of alternator tube M5. The start key 23 at its contacts 213 also interrupts the holding circuit for the release relay I50 toeffect the restoration thereof.

Release relay I50 restores, closing the loop to land the call in the switchboard at contacts I55; at its contacts I5I interrupts a point in a self holding circuit; and at its contacts I52 connects ground to the P wire of the outgoing conductor I82 (which has significance under certain circumstances such as illustrated in Figure 101)). Release relay I50 at its contacts I53 interrupts the application of positive biasing potential to grid 418 of the stop tube 415 in preparation for the extinguishment thereof; and at its contacts I54 effects application of positive potential to the control grid 301 of the second generator tube 305 over a circuit extending from positive battery, contacts I54, conductor I51, the RC circuit comprising resistance 244 in parallel with capacitor 245, contacts 2I1 of the repeat key, conductor 215, and the RC network comprising resistances 312a, 3121), 314b, 3140, 311 and capacitor 318.

A differentiated pulse is applied by the described components to the control grid 351 of the second generator tube 305 to effect firing of same.

Release relay I50 at its contacts I54 are also effective to connect positive potential over the winding of the reset relay 250, and conductor 212 to plate 48! of the start tube 480. Additionally, release relay I50 at its contacts I54 effects the application of positive potential over conductor IQI and 214 to the plates of each of the tubes in sequence chain 54.

Release relay I50 at its contacts i54 also effects the application of the starting impulse to the start tube 480, the pulse being applied over contacts I54, conductor EQI, the RC network comprising resistances 256, 251, 258 and 25B and capacitor 264 as interconnected by contacts 262 and contacts 255; contacts 223, conductor 21s, and resistance 481 to the control grid of start tube 480.

It is noted that the starting potential rise is controlled by the pause adjustment network, whereby the period of delay between the time of operation of the start key and the operation of the start tube 480 may be adjusted to various predetermined values, the adjustment being accomplished by movement of the variable resistor 258.

As the positive potential rise is applied to the grid 483 of start tube 480, the tube 480 is rendered conductive and an energizing circuit is completed for reset relay 250, the circuit extending from positive battery over contacts I54, conductor 13!, reset relay 250, conductor 212, and the conducting start tube 580 to negative battery.

Stop tube 415 is extinguished as a result of the drop of potential at the plate 416 thereof as the start tube 480 fires and effects transfer, over capacitor 488, of the potential drop appearing at plate 48L Reoperation of the stop tube 415 is prevented in that contacts I53 are open, and positive potential is no longer applied to the control grid 478 of the stop tube.

Reset relay 250 operates, and at its contacts 25I interrupts the source of positive potential for the control grid 313 of the now conductive alternator tube 3I0.

4.43 Impulse generation Reset relay 250 at its contacts 252 connects positive potential over conductor 210 to the generator control RC network 315 to effect the application of a positive operating pulse to initiate operation of the generator unit 50 to generate a series of impulses in the manner described heretofore is immediately effected. With tube 305 previously fired, tube 300 thereupon fires.

Reset relay 256 at its contacts 254 connects capacitor 264 to negative battery over resistance 255 to effect the discharge thereof, so that with the subsequent recycling of the equipment, capacitor 264 is in the discharged condition and the desired pause between cyclings of the equipment may be eifected.

As the generator tube 300 strikes responsive to application of positive potential to lead 210, a negative impulse is applied over capacitors 38I and 322 squelching tube 305. The firing of tube 308 also completes an operating circuit for the pulsing relay I in the manner heretofore described.

Pulsing relay I00 operates and at its contacts 152 initiates transmission of a portion of the first pulse, the open period with pulse key 28 is in the break position as assumed (the closed period of pulse key 28 is in the make position). After a predetermined time period (which is established by the positions of the speed and break control keys I8 and I9) has expired, the control grid 301 is driven positive and generator tube 305 fires. Simultaneously the extinguishment of the first generator tube 30-0 is effected. The pulse relay I60 releases to terminate the first portion of the first impulse and to initiate the second portion thereof.

It is apparent that the generator tubes 300 and 305 will continue to operate in a cyclic and alternative manner for the period that operating potential is appl'ed to network 315 by the operative reset relay 258. The pulsing relay operates opening the line loop with each striking of generator tube 305 and releases closing the line loop with the extinguishing of tube 300.

Each time that generator tube 300 is extinguished, the potential at its plate 30I rises to approximately 50 volts and a positive impulse is transmitted over the interconnecting circuit elements to the alternator unit 5|.

4.44 Alternator operation for the best operation of the alternator. Also 

